Patterns of presentation of the shaken baby syndrome Four
types of inflicted brain injury predominate

EDITOR-One of the controversies that has recently arisen in cases of
alleged shaken baby syndrome concerns the disparity between certain
neuropathological findings at necropsy and whether these findings are
consistent with the entity regarded as the shaken baby syndrome.
A database was collected for more than five years of documented Scottish
cases of suspected non-accidental head injury diagnosed after a multiagency
assessment and including cases with uncoerced confessions of perpetrators
and criminal convictions. Several patterns of presentation allow
delineation of cases into four predominant types.

Hyperacute encephalopathy (cervicomedullary syndrome)
This hyperacute encephalopathy (6% of all cases) results from extreme
"whiplashing" forces, the infant suffering the equivalent of a broken neck
or, more correctly, a broken brain stem. In infants with a median survival
of one day Geddes et al described localised axonal damage at the
craniocervical junction, in the corticospinal tracts, and in the cervical
cord roots, consistent with hyperflexion and hyperextension movements.1
These cases, which truly reflect a "whiplash" shaking injury to the stem,
are infrequently seen by clinicians because the patients are either dead on
admission or die shortly thereafter.

Presentation is at 2-3 months of age, with acute respiratory failure
(direct medullary trauma) and cerebral oedema (a "black brain" on imaging).
At necropsy these infants have severe brain swelling and hypoxic injury but
little axonal shearing and only a thin (trivial) subdural haemorrhage. Such
presentations could result from a primary injury to the brain stem, induced
by hyperflexion and hyperextension, or, rarely, from traumatic thrombosis
of the vertebral arteries in the foramina of the cervical vertebrae.

Acute encephalopathy
An acute encephalopathic presentation (53% of cases) is characterised by a
depressed conscious state, raised intracranial pressure, fits, apnoea,
hypotonia or decerebration, anaemia, shock, bilateral subdural haematomas,
and widespread haemorrhagic retinopathy. Coexistent rib fractures,
metaphyseal fractures, or other non-accidental injuries may be found. This
is the commonest presentation seen by paediatricians and is referred to as
the classic shaken baby syndrome (repetitive rotational injury). Depending
on whether additional signs of impact are noted (focal subdural,
extradural, or subgaleal haemorrhage; scalp injury; or skull fracture), the
syndrome has been referred to as the shaken impact syndrome.

The brain injury is well documented from studies of magnetic resonance
imaging,2 which show widespread vascular shearing with convexity subdural
haemorrhages enlarging over the first week (as well as interhemispheric,
subtemporal, suboccipital, and posterior fossa subdural haemorrhages), torn
bridging veins, cerebral oedema, haemorrhagic contusions and lacerations,
and white matter shearing, with tears and petechial haemorrhages at the
junction between grey and white matter and in the corpus callosum. Up to
60% of cases have serious long term morbidity.

Subacute non-encephalopathic presentation
In infants with a non-encephalopathic subacute presentation (19% of cases)
the brain injury is less intense, without swelling, diffuse cerebral
hypodensities, or clinical encephalopathic features. These children have
various combinations of subdural and retinal haemorrhages, rib fractures
and other skeletal fractures, bruising, etc. The outcome in this group is
better.

Chronic extracerebral presentation
A chronic extracerebral presentation (22% of cases) is seen in children of
a few months of age who present with an isolated subdural haemorrhage,
which is often chronic (> 3 weeks) and late in presenting. A rapidly
expanding head circumference and signs of raised intracranial tension are
common: the child may be irritable, vomiting, failing to thrive, hypotonic,
fitting but with little encephalopathy.

The primary injury is extracerebral but with potential secondary injury
from raised intracranial pressure and reduced cerebral perfusion pressure
and hypoperfusion, oedema, and metabolism to flow mismatch in the white
matter.3 Any retinal haemorrhages originally present have disappeared by
presentation. The injury has occurred weeks earlier, and its force has been
sufficient to rupture the weakest bridging vein(s) but insufficient to
produce an acute encephalopathy. The prognosis is good with recognition and
appropriate treatment.

Clinicians will have difficulty in attributing a causative mechanism and
timing to such late presenting (idiopathic) subdural haemorrhages. Only in
the presence of residual features of physical abuse (such as fractures),
along with identifiable risk factors, would non-accidental injury be
considered. Most cases remain aetiologically unexplained, although trauma
remains the likely cause, but they are unlikely to be legally pursued
beyond medical investigations and social work inquiry.

Conclusions
We postulate that a spectrum of clinical features is related to the
intensity and type of injury in babies with inflicted brain injury,
reconciling the clinical and neuropathological findings. Infants can be
traumatically injured in many ways, and many instances are unwitnessed.
Thus the generic term non-accidental head injury or inflicted traumatic
brain injury should be used in preference to shaken baby syndrome, which
implies a specific mechanism of injury.

After the history, examination, and investigations have been considered the
following conclusions about the cause of brain injury can be reached: It is
characteristic of, consistent with, possibly due to, or not the result of,
non-accidental trauma.

Robert A Minns, consultant paediatric neurologist

Child Life and Health, University of Edinburgh and Royal Hospital for Sick
Children, Edinburgh EH9 1LF Robert.Minns@ed.ac.uk